The Components of The System Unit
is a case that contains electronic components of the computer used to process data
The System Unit
Drive Bay(s)
Power supply
Sound card
Video card
Processor
Memory
Processor
The processor, also called the central processing unit (CPU)
Multi-core processor
Dual-core processor
Quad-core processor
The control unit is the component of the processor that directs and coordinates most of the operations in the computer
The arithmetic logic unit (ALU) performs arithmetic, comparison, and other operations
The processor contains registers, that temporarily hold data and instructions
The system clock controls the timing of all computer operations
A processor chip generates heat that could cause the chip to burn up
Require additional cooling
Heat sinks
Liquid cooling technology
Data Representation
Analog signals are continuous and vary in strength and quality
Digital signals are in one of two states: on or off
Most computers are digital
The binary system uses two unique digits (0 and 1), Bits and bytes
ASCII (American Standard Code for Information Interchange) is the most widely used coding scheme to represent data
Memory
Memory consists of electronic components that store instructions waiting to be executed by the processor, data needed by those instructions, and the results of processing the data
Stores three basic categories of items
The operating system and other system software
Application programs
Data being processed and the resulting information
Each location in memory has an address
Memory size is measured in kilobytes (KB or K), megabytes (MB), gigabytes (GB), or terabytes (TB)
The system unit contains two types of memory
Volatile memory, Loses its contents when power is turned off, RAM, RAM chips usually reside on a memory module and are inserted into memory slots, Three basic types of RAM chips exist, Dynamic RAM (DRAM), Static RAM (SRAM), Magnetoresistive RAM (MRAM), The amount of RAM necessary in a computer often depends on the types of software you plan to use
Nonvolatile memory, Does not lose contents when power is removed, Flash memory can be erased electronically and rewritten, CMOS technology provides high speeds and consumes little power
Read-only memory (ROM) refers to memory chips storing permanent data and instructions
Firmware
Memory cache speeds the processes of the computer because it stores frequently used instructions and data
A PROM (programmable read-only memory) chip is a blank ROM chip that can be written to permanently
EEPROM can be erased
Access time is the amount of time it takes the processor to read from memory
Measured in nanoseconds
Expansion Slots and Adapter Cards
An expansion slot is a socket on the motherboard that can hold an adapter card
An adapter card enhances functions of a component of the system unit and/or provides connections to peripherals
Sound card and video card
With Plug and Play, the computer automatically can configure adapter cards and other peripherals as you install them
Removable flash memory includes
Memory cards, USB flash drives, and PC Cards/ExpressCard modules
Ports and Connectors
A port is the point at which a peripheral attaches to or communicates with a system unit (sometimes referred to as a jack)
A connector joins a cable to a port
A USB port can connect up to 127 different peripherals together with a single connector
You can attach multiple peripherals using a single USB port with a USB hub
Other types of ports include
Firewire port
Bluetooth port
SCSI port
eSATA port
IrDA port
Serial port
MIDI port
Buses
A bus allows the various devices both inside and attached to the system unit to communicate with each other
Data bus
Address bus
Word size is the number of bits the processor can interpret and execute at a given time
Expansion slots connect to expansion buses
Common types of expansion buses include
PCI bus
PCI Express bus
Accelerated Graphics Port
USB and FireWire bus
PC Card bus
Bays
A bay is an opening inside the system unit in which you can install additional equipment
A drive bay typically holds disk drives
Power Supply
The power supply converts the wall outlet AC power into DC power
Some external peripherals have an AC adapter, which is an external power supply
Keeping Your Computer or Mobile Device Clean
Clean your computer or mobile device once or twice a year
Turn off and unplug your computer or mobile device before cleaning it
Use compressed air to blow away dust
Use an antistatic wipe to clean the exterior of the case and a cleaning solution and soft cloth to clean the screen
Putting It All Together
Home
Intel Core 2 Duo or Intel Celeron Dual Core or AMD Sempron
Minimum RAM: 2 GB
Small Office/ Home Office
Intel Core 2 Quad or Intel Core 2 Extreme or AMD Athlon FX or AMD Athlon X2 Dual-Code
Minimum RAM: 4 GB
Mobile
Intel Core 2 Extreme or AMD Turion X2
Minimum RAM: 2 GB
Power
Intel Itanium 2 or AMD Quad Core Opteron or Intel Quad Core Xeon or Sun UltraSPARC T2
Minimum RAM: 8 GB
Enterprise
Intel Core 2 Quad or Intel Core 2 Extreme or AMD Athlon FX or AMD Athlon X2 Dual-Core
Minimum RAM: 4 GB
